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Networking Fundamentals · Intermediate

Three-Tier Architecture

A hierarchical campus design with core, distribution and access layers, each with distinct roles.

Definition

The access layer connects end devices, the distribution layer aggregates access switches and applies policy and routing between VLANs, and the core provides fast, highly available transport between distribution blocks. The hierarchy improves scalability and fault isolation.

Example

A large campus has access switches per closet, distribution switches per building and a core in the data center.

Exam tip

Policy belongs at distribution; the core should only switch fast.

Don't confuse it with

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